The present invention relates to a mass spectrometric apparatus.
Generally, in a mass spectrometric apparatus, first a sample to be analyzed is ionized, and then a superposed electric field is so scanned that ions of the samples are passed in the order of their mass numbers. A mass spectrum is obtained by detecting the ions that are output in the order of their mass numbers. This type of technology is described on pages 4-11 of Fuwa and Fujii, "Quadrupole Mass Spectrometer, its Principle and Applications" (in Japanese), Kodansha Ltd., Publishers, 1984.
In a mass spectrometric apparatus, it may be the case that a large amount of ions reach the detector simultaneously. For example, in a liquid chromatograph mass spectrometric apparatus, ions corresponding to a moving phase simultaneously reach a detector when an electric field is so set as to allow passage of ions having a mass number corresponding to the moving phase. Also in a plasma ion mass spectrometric apparatus, ions of argon simultaneously reach a detector when an electric field is so set as to allow passage of, for instance, argon gas.
If a large amount of ions reach the detector simultaneously, the detector is saturated instantaneously and unable to detect subsequent small peaks. Further, if this saturation phenomenon occurs repeatedly, the detection sensitivity is deteriorated by an accumulation effect to hinder detection of a sample of a very small quantity.